Two-speed supercharger drive



July 6, 1943. L.. s. HOBBS TWO-SPEED SUPERCHARGER DRIVE 5 Sheets-Sheet 1 Filed Jan. 10, 1940 INVENTOR IHII 5 B. B O H .m A17. N. o. E LM E N R o n A July 6, 1943. L. s. HOBBS 2,323,501

TWO-SPEED SUPERCHARGER DRIVE Filed Jan. 10, 1940 5 Sheets-Sheet 2 INVENTOR LEONARD S.HOBBS 8Y4? kg ATI'ORINEY J ly 6, 9 3- L. s. HOBBS TWO-SPEED SUPERCHARGER DRIVE Filed Jan. 10, 1940 5 Sheets-Sheet 4 ATTORNEY July 1943. L. s. HOBBS TWO-SPEED SUPERCHARGER DRIVE- 5 Sheets-Sheet 5 Filed Jan. 10, 1940 LEONARD s. HOBBS 5W 4% ATTORNEY Patented July 6, 1943 TWO-SPEED SUPER I GER DRIVE Leonard S. Hobbs, West Hartford, Conn., assignor to United Aircraft Corporation, East Hartford, Court, a corporation of Delaware Application January 10, 1944), Serial No. 313,231

(oi. id-189.5)

6 Claims.

This invention relates to improvements in change speed gear drives or power transmissions and has particular reference to a change speed gear drive or transmission for a rotating body such as a fan or supercharger impeller although the principles of the invention are in no way limited to this particular application.

An object of the invention is in the provision in a change speed drive gear of means for synchronizing the gears of the various speed ratio gear trains when the drive is changed from one train to another.

A still further object resides in the provision of an improved change speed gear drive in which a single hydraulic synchronizing unit is utilized to synchronize the speeds of the driving and driven elements of the various speed ratio gear trains as the drive is transferred to any one of said gear trains.

Other objects and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the accompanying drawings, in which like reference numerals are used to indicate similar parts throughout, there is illustrated in two slightly difierent forms a suitable mechanical embodiment for the purpose of disclosing the invention. The drawings, however, are for the purpose of illustration only and are not to be taken as limiting the invention since it will be apparent to those skilled in the art that various changes in the illustrated constructions may be resorted to without in any way exceeding the scope of the invention.

In the drawings,

Fig. 1 is a schematic view of a change speed gear of the character indicated applied to the supercharger impeller drive of an internal combustion engine.

Fig. 2 is a rear elevation of a modified form of supercharger drive.

Fig. 3 is a. sectional view of an enlarged scale on the line 3-3 of Fig. 2.

Fig. 4 is a sectional view on an enlarged scale on the line 3- of Fig. 2.

, Fig. 5' is a sectional view on an enlarged scale of the change speed gear drive of Fig. 1.

Fig. 6 is a longitudinal sectional view of a control valve for the change speed gear unit shown in Figs. 2 to 5, inclusive.

Fig. 7 is a sectional view of a fragmentary portion of the valve unit shown in Fig. 6 taken on the line I--l of Fig. 6.

Figs. 8, 9, 10, and 11 are diagrammatic sketches showing the hydraulic connections for the various operative positionsof the valve shown in Fig. 6.

Referring to the drawings in detail and particularly to Fig. l the numeral l0 generally indicates the crankcase of an internal combustion engine, such as a radial type supercharged engine conventionally employed for the propulsion of aircraft; It is to be understood, however, that the invention is'in no way limited to any particular type of engine or to the illustrated application to an engine supercharger drive.

In the engine illustrated the crankcase It may carry a plurality of cylinders, one of which is indicated at l2, connected to the supercharger blower section It by respective intake ducts, as

Y indicated at i6, and may drive an aeronautical .and directs it at increased pressure to the diffuser 26. The impeller 22 may be mounted on an impeller drive sleeve 28 rotatably supported in the casing 20 by suitable means such as the bearing 30 and the shaft 36 which is supported by the bearing 32 and crankshaft 36. The impeller may be driven from the engine crankshaft 34! by means of a tail shaft 36 and a change speed gear drive including a plurality of gear trains, as indicated at 38, 40 and 42. The gear train 38 may constitute a permanent driving connection between the tail shaft 36 and the lay shafttt and the gear trains 40 and 32 may constitute different speed ratio drives between the lay shaft and the impeller drive sleeve 28.

The various units of the change speed gear drive such as the various gear trains and their connecting clutches and the synchronizing device may all be mounted on the same shaft, as schematically indicated in Fig. 1 and shown in detail in Fig. 5, .or these various units may be mounted on separate shafts, as shown in Figs. 2, 3 and 4. As an example of the latter arrangement the tail shaft 36 and gear train 38 may occupy the central position in the arrangement shown in Fig, 2 and the drive gear on the tail shaft may mesh with separate drive gears on three different lay shafts, as indicated at 46. 48 and 50. As shown in Figs. 3 and 4, the low speed gear train 42 may be disposed between the centrally disposed lay shaft 48 and the impeller drive sleeve surrounding the tail shaft 38, the high speed gear train 40 may be disposed between the lay shaft and the impeller drive sleeve while the synchronizing device, generally indicated at 5|, may be disposed between the lay shaft 50 and the impeller drive sleeve.

Referring now particularly to Figs. 3 and 4, the tail shaft 36 carries a drive gear, generally indicated at 52 which meshes with driven gears 54, 56 and 58 carried by the lay shafts '46, 48 and 50, respectively, so that all three of the lay shafts rotate with the tail shaft when the engine is operating. The gear 52 may be formed in two parts one of which, as indicated at 60, carries the gear teeth and the other, as indicated at 62, is secured to the shaft 36 by suitable means such as the spline 64. The two parts 60 and 62 are drivingly connected by means of a plurality of spring packs 66 to provide a spring cushioned drive between the tail shaft 36 and the lay shaft gears 54, 56 and 58 in a manner well known to the art.

A spur gear 68 is carried by the lay shaft 48-for free rotation relative thereto and has peripheral teeth which mesh with the peripheral teeth of a low speed drive gear formed integrally with or rigidly secured on the impeller drive sleeve 28. The gear 68 is provided with an annular flange 12 which may carry internally thereof a clutch facing 14 to constitute one element of a clutch by means of which the gear 68 may be associated with the shaft 48 against rotation relative thereto. The other portion of this clutch is consti tuted by a member 16 having a slidable splined connection with the shaft 48 and a tapered flange underlying the clutch facing 14 and operative to frictionally engage the clutch facing upon movement of the member 1.6 axially of the shaft 48 in a direction away from the associated gear 68, the gear element 68 being restrained from axial movement along the shaft by suitable means such as the bearing bushing 18 cooperating with an annular shoulder 80 formed on the shaft 48. A compression spring 82 bearing at one end against the clutch element 16 and at its other end against the annular abutment 84 resiliently urges the member 16 towards the gear 68 to disengage the clutch and permit the gear to rotate freely on the shaft 48. Within the space between the gear 68 and the clutch element 16 a fluid seal 86, carried by a flange member 88 rigidly secured to the gear 68, cooperates with a cylindrical surface 90 provided within the flange of the member 16 to provide an annular fluid chamber 92 surrounding the shaft 48 within the members 68 and 16 to which "fluid under pressure is directed, forcing the members 16 and 68 apart to engage the clutch and provide a drive between the shaft 48 and the impeller drive sleeve 28. The chamber 92 may be supplied with fluid under pressure through the channels 94 and 96, theannular groove 98 leading around the impeller drive sleeve 28, and the channels I00 and I02 in the drilled plug I04 inserted in the end portion of the hollow shaft 48. and the port I06 leading from the channel I02 through the hollow shaft to the annular chamber 92. The remaining channels and ports shown in the plug I04 and the shaft 48 are for the purpose of supplying lubricating oil to the end bearings of the shaft.

The lay shaft 46 carries a clutch and gear arrangement similar to that carried by the shaft 48 and described above. As shown in Fig. 4, a gear I08, freely rotatable on the shaft 46 but restrained from axial movement thereon, has

peripheral teeth which mesh with the teeth of the high speed drive gear IIO integral with the impeller drive sleeve 28. This gear has an integral flange II2 which carries a clutch facing a clutch'element II8 rotatable with the shaft 46 by reason of the spline connection I20, and slidable along the shaft in one direction by the spring I22 and in the other direction by fluid pressure in the annular chamber I24 sealed by the packing I26 carried'by the annular flange member I28. Fluid under pressure is supplied to the chamber I24 through a channel I30 in the casing 20 and channels I 32 and I34 in the plug I36 and ports I38 in the hollow shaft 46 leading from the chan nels I32 and I34 to the annular space I24,

The hydraulic coupling unit'or synchronizing accelerator, generally indicated at 5|, is carried by the layshaft 50 and has one portion I 40 drivingly connected with this shaft through the spline connection I42 and a second portion including the elements I44 and mounted upon the shaft by the bearing bushings I48 and I50, the portion I44 being provided with peripheral gear teeth which mesh with the teeth of a gear I52 formed on the impeller drive sleeve 28 and having a diameter less than the diameter of either of the ears 10 or H0. The coupling 5| may be of a general character well known to the prior art, and commonly known as the Hittinger type of hydraulic coupling. In general. the elements I40 and I46 when associated in the relation illustrated constitute a toroidal chamber one-half of which is connected to the shaft 60 and the other half of which is drivingly associated with the gear I52. Within the toroidal chamber there is an annular core I54 of substantially circular section split into two annular parts one of which is carried by the member I 40 and the other by the member I46. A plurality of radial vanes I56 are disposed in the space between the member I40 and the associated portion 1 the toroidal chamber the element I40 rotating with the shaft 50 will exert centrifugal force on the fluid causing it to circulate about the core I54. This movement of the fluid exerts a force on the portion of the coupling including the members I44 and I46 and causes this portion to rotate .with the element I40, the fluid connection between the two portions of the coupling being uniform and flexible so that no sudden impulses are imparted to the driven portion but its speed is gradually increased to near the speed of the driving portion. For the purposes of this disclosure it may be said that such a coupling tends to operate with an extremely small slip, that is,

I46 rotatably small speed difference between the driving and driven elements, after the initial starting effort on the driven portion has been accomplished. Fluid is supplied to the toroidal chamber through the conduit I60, the drilled passages I62 and I64 in the plug I66 inserted in the end of the hollow shaft 50 and the ports I68 leading through the hollow shaft to the passages I10 extending through the inner portion of the coupling element I40 to the annular chamber.

The ends of the shafts 46 and 60 may be provided with driving gears I12 and I14 splined thereto if desired, to which other engine accessoriessuch as magnetos or generators may be operatively connected.

The flow of fluid to the gear clutches and the accelerator is controlled by a manually operable valve I16 and particularly illustrated in Fig. 6. of which comprises the double cylinder I18 and the other part the detachable cylinder head I80- The portion In includes a hydraulic cylinder I82, in which the piston I84 is reciprocable, and an integral cylindrical ported valve casing I88, concentric with the cylinder I82, in which the valve plunger, generally indicated at I88, is reciprocable. When the valve I16 is operatively associated with an engine the valve casing I86 is inserted in a suitable aperture provided in some portion of the engine crankcase I0. The fluid conduit 94 for the low speed clutch leads through the engine crankcase to a port I90 in the valve cylinder I86. Similarly the conduit I30, connected with the high speed clutch, leads to a port I92 in the valve cylinder, and the conduit I60, connected with the hydraulic accelerator or synchronizer 5|, is provided with two branches leading to ports I84 and I96 in the valve cylinder, I86. The valve cylinder also includes a drain channel I98, connected with a drain conduit 200, and connected with the interior of the valve cylinder by the elongated slot 202.

The cylinder head I80 carries a rotatable shaft 286 the ends of which project beyond the exterior of the cylinder head and to one projecting end of which is secured the manually actuatable valve operating lever 208. Within the cylinder head the shaft 200 is provided with a radial arm 2I0 connected by suitable means, such as the link 2I2, with a movable abutment 2I4 slidable in the hollow valve plunger I88 and resiliently urged towards the end of the adjacent end of the plunger I88 by the coiled compression spring 2 I6. The hollow valve plunger I88 is formed integrally with or rigidly secured to the piston I84 and may be divided into a number'of separable parts if desired, for convenience in manufacture and assembly. Fluid under pressure is fed into the valve chamber through the conduit 2 I 8, and flows through the hollow valve member I88 and out through the ports 220 in the member 2 I4 into the cylinder I82 where it may flow through the flap valves 222 to fill up the cylinder on both sides of the piston I80- Some of the fiuidin the cylinder- I82 may flow through the aperture 226 into the chamber 228 and through the conduit 230 and valve 234 controlled by the thermostat 232 to the drain channel I98, the purpose of this lead being to permit replacement of low temperature fluid in the cylinder I82 by warm fluid from the engine lubricating system. The thermostat 232 will close the valve 234 and cut oil the flow of oil from the cylinder I82 to drain when the fluid in the cylinder is at the proper temperature. 2

The operation of the device is substantially as follows:

Assuming the valve member I88 and piston I84 to be in the left-hand position, as shown in Fig. 6, the valve will be in its neutral position with the pressure port 224 cut off and the lines 94-, I30 and I60 connected with the drain channel I98 and drain line 200, through the slot 202 and groove 236 in the plunger I88, as is particularly illustratedin Fig. 6. Under these conditions both clutches and the hydraulic synchronizer will be free of fluid and there will be no driving connection between the tail shaft36 and the super- This valve has a two part casing one part into alignment with the port I94, leading to the .manually actuated to the low speed drive position. Actuation of the lever 208 will rotate the shaft 206 and swing the arm 2I0 to move the link 2I2 in a direction to force the abutment 2I4 to the right compressing the spring 2 I 6. The piston I84, however, will not immediately follow the movements of the abutment 2 because of the fluid caught between the piston and the right hand end of the cylinder I82. However, the force of the spring 2 I 6 will urge the piston to the right, as viewed in Fig. 6, and the fluid in the space to the right of the piston will flow slowly through the bleed opening 238 in the piston, permitting the piston and the valve member I88 to move slowly to the right. As the valve plunger moves to'the right the pressure port 224 will first come hydraulic synchronizer or accelerator through the conduit I60. Fluid under pressure will then flow from the valve to the accelerator and, by proper adjustment of the time interval of fluid application, render the accelerator operative only long enough or efliciently enough to absorb the work required to gently start the impeller and without sudden impulse bring its speed up substantially equal to or slightly above the speed at which it is driven by the low speed drive, this position of the valve being diagrammatically shown in Fig. 8. As the movement of the piston and valve member to the right continues the port 224 will move out of register with'the port is particularly shown in Fig. 9, the high speed drive conduit I30 being connected with the drain channel 200 through the annular groove 236. The movement of the piston and valve member to the right will be limited by the position of the abutment 2I4 as controlled by the position to which the shaft 206 is brought by the manual control and this limiting position will be such that the pressure port 224 will remain in registry with the port I90 to continue the supply of fluid under pressure to the low speed clutch as long as operation of the low speed drive is desired.

When it is desired to shift from the low speed to the high speed drive the manual control 208 is again actuated to bring the abutment 2I4 to the high speed drive position, again compressing the spring 2I8 to exert a resilient force on the valve member I08 and piston I84. As the fluid to the right of the piston again flows out through the bleed opening 238, movement of the valve member to the right will be resumed to first bring the groove 240 into register with the port I90 to drain the low speed clutch and release the low speed drive. Immediately after the low speed drive has been connected with drain the pressure port comes into registry with the fixed port I96 to again apply fluid to the hydraulic synchronizer or accelerator, the position of full registry being diagrammatically shown in Fig. 10. This application of fluid to the accelerator 5| will be of suflicient duration to absorb the work required to increase the speed of the impeller without sudden impulse, this time to a speed equal to or somewhat above the speed at which the impeller will be drivenby thehigh speed drive. As shown in Fig. 4, the gear I52 is somewhat smaller than the high speed drive gear IIO I in order to provide a gear ratio between the impeller and the accelerator somewhat greater than the ratio of the high speed drive to compensate for the slip of the hydraulic coupling 5| and render this coupling capable of bringing the impeller up to the full speed of the high speed drive. Continued movement of the valve member I88 to the right under the influence of the compressed spring 2I6 will then move the pressure port 224 out of register with the port I96 and into registry with the port I92 leading to the conduit I30 to apply fluid pressure to the high speed drive clutch. As the port 224 moves into registry with the port I92 the groove 240 moves into position to cover the port I96 to connect the conduit I60 with the drain line, in addition to the conduit 84 which has already been connected with drain,

as explained above, to free the low speed drive and the accelerator and limit-the drive to the high ratio gear train, the position of the valve for the high speed drive being particularly illustrated in Fig. 11. The valve may be left in the position shown in Fig. 11 as long as the high speed drive is desired.

The drive may be shifted from the high speed to the low speed drive by a reverse movement of the manual control moving the valve member I 88 to the left. When such a movement i imparted to the valve member the flap valves 222 will permit rapid flow of fluid from the left hand to the right hand side of the piston I84 so that the drive.

is transferred almost immediately from the high speed to the low speed gear train, thaction of the synchronizer being substantially omitted since the air resistance on the impeller will quickly bring the impeller down to the low gear ratio speed and the action of the synchronizer is not needed. In the same manner the valve may be returned to the neutral position illustrated in Fig. 6.

It is thus apparent that a change speed transmission has been provided which is operative under manual control to automatically shift the drive from one gear ratio to another and to match the speeds of the drivin and driven elements as the drive is shifted from a lower to a higher ratio connection.

The automatic operation of the control valve and the timing of the synchronizing action by the piston I84 and the bleed port 238 and the resilient connection between the control valve I88 and the manual control lever 208 are all claimed in the co-pending application of Gunberg, Serial No.. 320,710, filed February 24, 1940.

The cylinder head I80 may be secured to the cylinder I18 and the member I18 may be secured in place on the crankcase I0 by suitable means, such as the through bolts 242, and the piston I84 and valve member I88 may be restrained against rotation inthe member I18 by suitable means, such as the'guide rods. one of which is indicated at 244.

Fig. 5 shows an arrangement in which the two gear drives and the synchronizing clutch are all mounted on the same shaft. In this arrangement a gear 246 on the tail shaft 36 drives a gear 248 splined on the lay shaft 250 so that the lay shaft is driven at all times at which the engine is in operation. Gear members 252 and 254, mounted on the shaft 250 for free rotation relative thereto, mesh with gear elements 256 and 258 respectively on the impeller driv sleeve 28, the elements 252 and 256 constituting a low speed drive while the elements 254-and 258 constitute a high speed drive. The elements 252 and 254 are provided with respective integral flanges 260 and 282 carrying clutch faces 264 and 266 with which the clutch faces of two flange members 268 and 210 may engage to provide driving connections between the shaft 250 and the sleeve 28, the members 268 and 210 being splined to the shaft 250 in such a manner that they are restrained from rotation relative to the shaft but are axially slidable along the shaft. The two clutch members 268 and 210 are disposed face to face and are urged apart by a compression spring 212 the resilient force of which tends to disengage both of the clutches and acts, whenever one of the clutches is engaged, to automatically disengage the alternative clutch. An annular fluid chamber 214 is provided between the gear elements 252 and the clutch element 268, and a similar chamher 216 is provided between the gear element 254 and the clutch element 210, the chambers beingrior of the hydraulic coupling 218 and with the conduit I60 leading from the control valve, with a second internal passage 286 connected with the chamber 216 and with the conduit I30, and with an external passage 288 disposed between a reduced end portion of the shaft and a bushing 290 and connected with the chamber 214 and the conduit 94. With this arrangement it is apparent that fluid under pressure from the control valve may be separately supplied to each of the clutch operating chambers 214 and 216 and to the hydraulic synchronizing coupling 218.

The operation of the mechanism shown in Fig. 5 under the actuation of the control valve is the same as that described above except that the coupling 218 drives the same gear 258 which is driven by the high speed drive gear 254. thus providing no compensation for slip of the hydraulic coupling. Thus, it is obvious that, while the coupling will be capable of bringing the speed of the drive sleeve 28 up to or above the speed at which it is driven by the low speed drive in-- cluding the gears 252 and 256, it may not be able to bring the speed of the drive sleeve quite up to the speed at which the sleeve would be driven by the high speed drive gear 254. However, since the slip of a coupling of the type illustrated is relatively negligible being in the neighborhood of three to five percent, it is apparent that this speed difference will impose no excessive strain on the clutch including the element 210 and clutch facing 266 when the drive is shifted to the high speed gear ratio.

While two slightly different mechanical embodiments have been hereinabove described and illustrated in the accompanying drawings for the purpose of disclosing the invention, it is to be understood that the invention is not limited to the particular constructions so illustrated and described, but that such changes in the size, shape and arrangement of the various parts may be resorted to as come within the scope of the sub-joined claims.

Having now described the invention so that others skilled in the art may clearly understand the same, what it is desired to secure by Letters Patent is as follows:

1. In a change speed gear drive having a driving member and a driven member, and a plurality of gear drives of different ratios between said members, a clutch associated with each gear drive to render the respective gear drive operative or inoperative, a single hydraulic coupling between said driving and driven members operative to accelerate said driven member from a lower to a higher speed, and a selector valve associated with said clutches and said coupling to render said clutches and said coupling operative in an order such that the driving connection maybe made through the hydraulic clutch before each coupling is engaged in a speed increasing direction.

2. The arrangement as set forth in claim 1 in which said clutches and said coupling are fluid actuated and individual fluid lines connect said friction clutches with respective ports in said selector valve.

3. A change speed transmission, including a driving element, a driven element, a plurality of gear drives of difierent speed ratios between said driving element and said driven element, a clutch associated with each gear drive to render the respective gear drives operative or inoperative, a' hydraulic coupling between said driving and driven elements in parallel with said gear drives operative to accelerate the speed of said driven element before the low speed gear drive is rendered operative, or when the drive is being changed from a lower to a higher speed ratio gear drive to relieve said clutches of the duty of accelerating said driven element, said friction clutches being hydraulically actuated, and a speed ratio selecting valve for connecting said clutches and said fluid drive to a source of fluid under pressure.

4. A change speed transmission, including a,

driving element, a driven element, a plurality of gear drives of difierent speed ratios between said driving element and said driven element,

.ratio gear drive to relieve said clutches of the duty of accelerating said driven element, and a common shaft on which allof said gear drives and said hydraulic coupling are mounted;

5. A change speed transmission, including a driving element, a driven element, a plurality of gear drives of different speed ratios between said driving element and said driven element, a clutch associated with each gear drive to render therespective gear drives operative or inoperative, a hydraulic coupling between said driving and driven elements in parallel with said gear drives operative to accelerate the speed of said driven element before the low speed gear drive is rendered operative, or when the drive is being changed from a lower to a higher speed-ratio gear drive to relievesaid clutches of the duty of accelerating said driven element, said hydraulic coupling and at least one of said gear drives being mounted on different shafts.

6. In combination, a change speed transmission including a driven member, a driving member, a plurality of gear trains of diiferent ratios between said driving member and said driven member, a fluid actuated friction clutch in each gear train, at least one hydraulic drive between said driving and driven members, and a hollow shaft for said clutches and said hydraulic drive,

(a source of hydraulic fluid under pressure and a drain, a selector valve connected with said source and said drain, and fluid channels connecting said valve with said clutches and said hydraulic drive and including a fluid distribution plug in said hollow shaft.

LEONARD s. HOBBS. 

